But residents may have a leg up because Chattanooga has been doing some pre-emptive spending that could result in keeping local rates lower than in other cities targeted by the U.S. Environmental Protection Agency and the Department of Justice.

Chattanooga officials already had spent or allocated about $80 million to meet new federal clean water requirements even before an agreement was reached to settle two lawsuits that now mandate the expenditure of another $250 million on the city sewer system plus another $1.2 million for penalties and penalty projects.

"We knew this was coming," said Jerry Stewart, director of the city's waste resources division. "We were trying to be prepared."

They also were trying to make it clear to EPA and the Department of Justice that they were seriously willing to stop polluting the Tennessee River with raw sewage overflows from the Moccasin Bend Sewage Treatment Plant and the sewage system leading to it.

Steve Leach, the city's administrator of Public Works, said Chattanooga also showed foresight when, about 10 years ago, it started gradual fee increases of about 3.5 percent a year, a move that also helped show federal regulators the city is serious about fixing sewer problems, he said.

Working early to get on the good side of federal regulators might help save money, some officials reasoned. Other cities already were staring at fixes and penalties far higher than what Chattanooga signed onto this week.

So when Chattanooga officials began nearly two years ago negotiating the agreement that finally was announced Tuesday, they were also studying similar agreements made between EPA and other cities such as Lexington, Ky.; Cincinnati, Ohio; Philadelphia, Pa.; Nashville; Knoxville; and Memphis.

And they were also already spending money.

With stiff EPA oversight of meeting the consent decrees -- the official name for the agreements between the city and the federal agencies -- Chattanooga officials understood that cost to fix the problem could become whatever was necessary to keep sewage out of rivers. The city has dumped 354 million gallons of raw sewage into the Tennessee River since 2005, records show.

Preemptive spending

An example of Chattanooga's pre-emptive spending is a $2 million modeling program the city purchased in recent years that allows sewage treatment system operators to play "what if" games with sewage pump designs, rain events and other scenarios.

"We read the consent decrees of other cities and every one of them required models," Stewart said. "So we went ahead and were proactive."

Last year, the city spent more than $20 million to upgrade sewers and pumping stations in Altamont and the Pineville Road areas. The city also already allocated $38 million in its capital budget this year for sewer fixes in anticipation of the consent decree coming out.

The city also put $5.6 million in the capital budget for stormwater, or water quality, fixes.

Government and conservation officials have said the overflows were often caused by stormwater runoff choking the city's combined sewer and stormwater pipes. So the city hiked its stormwater fees three years ago to help pay for improvements to its stormwater system and received a consent decree last year from the EPA on water-quality issues.

But the majority of the money for the sewer fixes will come from the city's sewer fund. The stormwater fee is separated into a water quality fund and, while there are other combined sewer and stormwater lines downtown, the rest of the city's stormwater system already is separate from the sewers.

Paying the piper

Even with Chattanooga's advance spending and incremental sewer rate increases for the past decade, the city's sewer rates are in line with the rates of most Tennessee cities and are far lower than the $34.16 monthly rate in Murfreesboro and the $58.63 monthly bill in Knoxville, according to Richard Beeland, spokesman for Mayor Ron Littlefield.

They also are lower than Charlotte's $30 monthly rate, Birmingham's $42 bill and Atlanta's $87 bill, according to a Chattanooga Public Works' interceptor sewer system budget presentation for fiscal 2013.

Chattanooga hasn't been alone as a violator of the Clean Water Act by releasing overflows of raw sewage to American rivers. And neither has it been alone is facing steep expenses to upgrade its sewage treatment plant and the miles of sewage and stormwater piping and pump systems -- some as old as the cities themselves.

Knoxville's tab is $530 million and, in some cities -- such as Nashville -- the estimates of repairs that ultimately were mandated in the settlements grew as post-agreement assessments and repairs began.

Sonia Harvat, spokeswoman for Metro Nashville Water Services, said her city's consent decree became effective in 2009. The total estimated cost of $400 million has now escalated to $1.5 billion.

"The early cost figures were rough estimates at the time of negotiation prior to an elaborate study and analysis being done," she said.

Since 2009, Nashville has spent $60 million toward its billion dollar bill. And while Nashville's user fees -- now $29.76 a month -- have not gone up yet, they likely will.

"A revenue study is under way to assess the need for rate adjustments based on cash flow needs for the program," Harvat said. "But the assessment is not yet complete."

One of the hardest-hit communities by federal sewer decrees has been Knoxville.

Jason Meredith, spokesman for the Knoxville Utility Board, said the utility was slapped with a $530 million consent decree in 2005. A few months later, the utility board hiked the sewer fee 50 percent, then did it a second time in 2007. The rates then went up 8 percent in 2009, 12 percent in 2011 and are expected to see a 12 percent increase each year until 2016, he said.

So far, Knoxville has spent $380 million to correct its problem and has 10 years in which to do it, Meredith said.

EPA spokeswoman Davina Marraccini said EPA does not have any guidance to assist municipalities in determining how to pay for the work required under the consent decrees.

"Each municipality is different, and they have taken different approaches," she said.